1. Field of the Invention
This invention relates to a vehicular AC generator adapted to prevent cooling ability from being deteriorated by crossover connection portions of each of turns of phase windings of a stator coil. More particularly, this invention relates to a coil winding structure for decreasing or omitting crossover connection portions of each of turns of phase windings of a stator coil.
2. Description of the Related Art
FIG. 8 is sectional diagram showing the configuration of a conventional vehicular AC generator.
The conventional vehicular AC generator is configured so that a Lundell-type rotor 7 is rotatably mounted within a case 3 consisting of an aluminum front bracket 1 and an aluminum rear bracket 2 by means of a shaft 6, and that a stator 8 is fixed to the inner wall of the case 3 in such a manner as to cover the outer periphery of the rotor 7.
The shaft 6 is rotatably supported by the front bracket 1 and the rear bracket 2. A pulley 4 is fixed to one end of this shaft 6, so that the rotating torque of an engine can be transmitted to the shaft 6 by means of a belt (not shown).
Slip rings 9 for supplying electric current to the rotor 7 are fixed to the other end of the shaft 6. A pair of brushes 10 are accommodated in a brush holder 11, which is disposed in the case 3, in such a way as to slide in contact with the slip rings 9. A regulator 19 for regulating the output voltage of the stator 8 is attached to a heat sink 17 fitted on the brush holder 11. A rectifier 12 electrically connected to the stator 8 and adapted to rectify an alternating current generated in the coil the stator 8 to a direct current is mounted within the case 3.
The rotor 7 comprises a rotor coil 13 which generates magnetic flux when an electric current flows therein, and a pair of pole cores 20 and 21 disposed so as to cover the rotor coil 13 in which magnetic poles are formed by the magnetic flux generated by the rotor coil 13. The pole cores 20 and 21 are made of iron, each has a plurality of claw-like magnetic pole pieces 22 and 23 circumferentially provided along the outer circumferential edge thereof at an equiangular pitch in such a way as to protrude therefrom. The pole cores 20 and 21 are fixed to the shaft 6 in such a manner as to face each other so that the magnetic pole pieces 22 and 23 engage with each other. Moreover, fans 5 are fixed to both axial ends of the rotor 7.
The stator 8 comprises a stator core 15 and a stator coil 16 composed of wires wound around this stator core 15 in which an alternating current is generated by alternating the magnetic flux of the rotor 7 owing to the rotation of the rotor 7.
In the conventional AC generator configured in this manner, an electric current is supplied from a battery (not shown) to the rotor coil 13 by means of the brushes 10 and the slip rings 9, so that the magnetic flux is generated. The claw-like magnetic poles 22 of the pole core 20 are magnetized to N polarities by this magnetic flux. The claw-like magnetic poles 23 of the pole core 21 are magnetized to S polarities by this magnetic flux. On the other hand, the rotatinal torque of the engine is transmitted to the shaft 6 by means of the belt and the pulley 4, so that the rotor 7 is rotated. Thus, a rotating magnetic field is given to the stator coil 16. Then, an electromotive force is generated in the stator coil 16. This AC electromotive force is transmitted to and rectified by the rectifier 12 to a direct current, its voltage is regulated by the regulator 18. Then, the battery is recharged.
The rotor coil 13, the stator coil 16, the rectifier 12 and the regulator 18 emit heat at all times during power generation. The heating values of these elements are 60 W, 50 W, 120 W and 6 W, respectively, at a high-temperature rotation point in the case of an AC generator of the class that has a rated output current of 100 A.
Thus, intake openings 1a and 2a and exhaust openings 1b and 2b are provided in the front bracket 1 and the rear bracket 2 so as to cool heat generated by power generation. As indicated by arrows in FIG. 8, at the rear side of the generator, outside air is sucked by the rotation of the fans 5 from the intake openings 2a respectively provided in such a way as to face a heat sink 19 of the rectifier 12 and the heat sink 17 of the regulator 18 and flows along the axis of the shaft 6. Consequently, the air cools the rectifier 12 and the regulator 18. Thereafter, each of the flows of the air is turned by the corresponding fan 5 to a centrifugal direction. Thus, the air cools the rearside coil end of the stator coil 16. Then, the air is discharged to the outside through the exhaust openings 2b. On the other hand, at the front side of the generator, outside air is sucked by the rotation of the fans 5 from the intake openings 1a in the axial direction. Thereafter, each of the flows of the air is turned by the corresponding fan 5 to a centrifugal direction. Thus, the air cools the front-side coil end of the stator coil 16. Then, the air is discharged to the outside through the exhaust openings 1b.
Next, the structure of the conventional stator 8 will be concretely described hereinbelow with reference to FIGS. 9 to 13. FIG. 9 is a rear elevation illustrating the coil connection employed in the conventional stator. FIG. 10 is a perspective view of a primary part of the conventional stator, viewed from the rear side thereof. FIG. 11 is a perspective view of the primary part of the conventional stator, viewed from the front side thereof. FIGS. 12 and 13 are schematic diagrams illustrating a method of winding the conventional stator coils.
The stator core 15 is formed like a cylinder and has a plurality of teeth 15a (each having a rectangular section) provided along the circumference thereof at an equiangular pitch in such a manner as to inwardly radially project therefrom. A slot 15b for accommodating the coil therein is formed between each pair of adjacent teeth 15a. Each of the slots 15b extends in parallel with the axial direction and is opened to the inner circumference of the stator core 15. In the case of this conventional generator, the rotor 7 has 12 magnetic pole pieces, and the stator 8 has 36 slots 15b. Thus, the number of slots per magnetic pole and per phase is 1.
Each of the stator coils 16 is constituted by (nearly U-shaped) coil pieces 30 as follows. Each of the coil pieces 30 has a pair of leg portions 30a connected by a nearly V-shaped connecting portion 30b. The leg portions 30a of each of the coil pieces 30 are inserted into two slots 15b, whose slot numbers are different from each other by three, from the rear side of the stator core 15. Then, open-end portions 30c extending toward the front side of the stator core 15 are joined together. Thus, the stator coils 16 are constructed. Incidentally, a coil conductor is constructed by connecting and integrating the coil pieces 30.
Two coil pieces 30 are inserted into each set of the two slots 15b, whose slot numbers are by 3, from the rear side of the stator core 15, as shown in FIG. 12. At that time, 4 leg portions 30a are accommodated in each of the slots 15b in such a manner as to be radially arranged in a line, as illustrated in FIG. 9. Further, the leg portions 30a of the outer-circumference-side coil piece 30 are inserted into a first place, which is closest to the outer circumference, in one of the slots 15b, whose slot numbers differ from each other by 3, and into the second place closest to the outer circumference, in the other slot 15b. On the other hand, the leg portions 30a of the innercircumference-side coil piece 30 are inserted into a third place, which is the third closest place to the outer circumference, in one of the slots 15b, whose slot numbers differ from each other by 3, and into a fourth place, which is the fourth closest place to the outer circumference, in the other slot 15b.
Moreover, after the leg portions 30a of each of the coil pieces 30 are inserted into the slots 15b as shown in FIG. 12, the open-end portions thereof extending toward the front side of the stator core 15 are bent in such a way as to outwardly open (that is, bent outwardly circumferentially). Furthermore, the open-end portion 30c of the coil piece 30 extending to the front side of the stator core 15 from the second outmost place in the corresponding slot 15b is made to overlap with the open-end portion 30c of another coil piece 30 extending to the front side from the first outmost place in another slot 15b, whose slot number differs from that of the former slot 15b by 3, as illustrated in FIGS. 11 and 13. Then, these open-end portions 30c are crimped with a clip 29. Subsequently, these open-end portions 30c are soldered to each other. Thus, two outer-circumference-side coils, each of which consists of the connected six outer-circumference-side coil pieces 30, are produced. Similarly, the open-end portion 30c of the coil piece 30 extending to the front side of the stator core 15 from the fourth outmost place in the corresponding slot 15b is made to overlap with the open-end portion 30c of another coil piece 30 extending to the front side from the third outmost place in another slot 15b, whose slot number differs from that of the former slot 15b by 3, as illustrated in FIGS. 11 and 13. Then, these open-end portions 30c are crimped with a clip 29. Subsequently, these open-end portions 30c are soldered to each other. Consequently, two inner-circumference-side coils, each of which consists of the connected six inner-circumference-side coil pieces 30, are produced.
Thus, in the two outer-circumference-side coils and the two inner-circumference-side coils inserted into adjacent two sets of two slots 15b selected at intervals of three slots, these coils are cut at the adjoining rear-side coil-end portions of these coils, as illustrated in FIG. 9. Subsequently, an end portion u1' of one of the inner-circumference-side coils is joined with an end portion u2 of one of the outer-circumference-side coils. Moreover, another end portion u2' of this outer-circumference-side coil is joined with an end portion u3 of the other inner-circumference-side coil. Furthermore, another end portion u3' of this inner-circumference-side coil is joined with an end portion u4 of the other outer-circumference-side coil. Thus, a four-turn coil corresponding to one phase is obtained. Further, the end portion u1 of the former inner-circumference-side coil is connected to the rectifier 12 as a lead wire. Moreover, the end portion u4' of the latter outer-circumference-side coil is connected to a neutral point in a star three-phase connection among this coil and coils respectively corresponding to other two phases.
Furthermore, similarly, the coils respectively corresponding to other two phases are produced.
Further, each of the u1'-u2 connection portion, the u2'-u3 connection portion and the u3'-u4 connection portion is not constituted by the connecting portion of the coil piece. Instead, these connection portions are formed outside the coil end portions, as crossover connection portions, as illustrated in FIG. 10. Incidentally, although three crossover connection portions are shown in FIG. 10, the stator actually has coils respectively corresponding to three phases. Thus, the stator has nine crossover connection portions.
In the case of the stator 8 constructed in this manner, the coil pieces 30 are inserted into the slots 15b from the rear side thereof. Moreover, the open-end portions 30c extending to the front side thereof are connected to each other as described above. Thus, the coil pieces 30 have almost the same shape. This results in increase in productivity of stators and easiness in being shaped after the fabrication thereof. Consequently, this reduces time and effort to perform the step of shaping the coil after the coil pieces are inserted into slots and connected to each other.
Moreover, connection portions for connecting the open-end portions 30c of the coil pieces 30 are concentrated at the front side of the stator. This enhances the workability in a process of connecting the open-end portions.
Incidentally, each of the nearly U-shaped coil pieces 30 is folded back nearly at the center of the corresponding connecting portion 30b. Both leg portions 30a of each of the coil pieces 30 are deviated from the folded-back portion in such a way as to suitably be accommodated in the slots 15b. Thus, each of the coil pieces 30 is inserted at a predetermined angle with respect to the circumference of the stator 8. Further, the longitudinal direction of each of the coil pieces 30 is a radial direction of the stator 8 at the folded-back portion thereof. In the slots 15b, one of the leg portions 30a is placed along a radius extending from the center of the stator core 15, while the other leg portion 30a is placed along a different radius of the stator core 15.
In this case of the stator 8 constructed in this manner, three crossover connection portions are necessary for connecting between 4-turn coils constituting each phase coil. Consequently, the conventional vehicular AC generator has a problem in that it is necessary for forming the crossover connection portions to cut, bend and draw the coil pieces 30 excessively and that thus, the workability thereof is deteriorated.
Thus, an improved stator structure for reducing the number of the crossover connection portions between 4-turn coils constituting each phase coil has been proposed.
FIG. 14 is a rear elevation illustrating the coil connection of an improved stator applied to a conventional vehicular AC generator. FIG. 15 is a perspective view of a primary part of the improved stator applied to the conventional vehicular AC generator viewed from the rear side thereof.
As shown in FIGS. 14 and 15, two coil pieces 30 are inserted from the rear side of the stator core 15 into each of the slots 15b whose slot numbers differ by three from each other. At that time, four leg portions 30a are axially arranged in a line and accommodated in each of the slots 15b. Further, two leg portions 30a of each of the coil pieces 30 are sequentially inserted into the second outermost place in a slot 15b and the third outermost place in another slot 15b, which is the third slot from the former slot 15b in the clockwise circumferential direction in FIG. 14. Moreover, two leg portions 30a of another coil piece 30 are serially inserted into the first outermost place in a slot 15b and into the fourth outermost place in another slot 15b, which is the third slot from the former slot 15b in the clockwise circumferential direction in FIG. 14, in such a manner as to stride over the connecting portion 30c of the coil piece 30 having leg portions precedingly inserted into the second outermost place in a slot 15b and into the third outermost place in another slot 15b, which is the third slot from the former slot 15b. Thus, the rear-side coil end portion is configured by stacking the connecting portions 30c of the coil pieces 30 as two layers as shown in FIG. 15.
Subsequently, in the case of each coil piece 30 having leg portions respectively inserted into the second outermost place in a slot 15b and into the third outermost place in another slot 15b, the open-end portions thereof extending from the slot 15b toward the front side of the stator core 15 are bent in such a way as to outwardly open, that is, bent outwardly. Furthermore, in the case of each coil piece 30 having leg portions respectively inserted into the first outermost place in a slot 15b and into the fourth outermost place in another slot 15b, the open-end portions thereof extending from the slot 15b toward the front side of the stator core 15 are bent inwardly.
Furthermore, the open-end portion 30c of the coil piece 30 extending to the front side of the stator core 15 from the second outmost place in the corresponding slot 15b, as indicated by dotted lines in FIG. 14, is made to overlap with the open-end portion 30c of another coil piece 30 extending to the front side from the first outmost place in another slot 15b, whose slot number differs from that of the former slot 15b by 3 in the counterclockwise circumferentially, as illustrated in FIG. 14. Then, these open-end portions 30c are crimped with a clip. Subsequently, these open-end portions 30c are soldered to each other. Similarly, the open-end portion 30c of the coil piece 30 extending to the front side of the stator core 15 from the third outmost place in the corresponding slot 15b, as indicated by dotted lines in FIG. 14, is made to overlap with the open-end portion 30c of another coil piece 30 extending to the front side from the fourth outmost place in another slot 15b, whose slot number differs from that of the former slot 15b by 3 in the clockwise circumferentially, as illustrated in FIG. 14. Then, these open-end portions 30c are crimped with a clip. Subsequently, these open-end portions 30c are soldered to each other.
Subsequently, the connecting portion 30b (thus, the rear-side coil end portions) is cut off from the coil piece 30 having leg portions respectively inserted into the second outermost place in one slot of the one set of the slots 15b, whose slot number differs from each other by three, and into the third outermost place in another slot 15b. Furthermore, the connecting portion 30b (thus, the rear-side coil end portions) is cut off from the coil piece 30 having leg portions respectively inserted into the first outermost place in one slot of the one set of the slots 15b, whose slot number differs from each other by three, and into the fourth outermost place in another slot 15b.
Then, end portions u2' cut off from the coil peace 30 is connected to end portion u3 of cut off from the coil peace 30. Thus, first and second coils each which consists of twelve connected coil pieces 30 are connected at this u2'-u3 connection portion. Consequently, a four-turn coil constituted by connecting 24 coil pieces 30 is obtained.
Further, end portions u1 and u4' of the coil pieces 30, which are cut off therefrom, respectively extend from the second and fourth places in the slots 15b to the rear side of the stator core 15, as illustrated in FIG. 15. The end portion u1 acts as a lead wire, and the end portion u4' is connected to a neutral point.
Furthermore, coils corresponding to other two phases are similarly produced. Further, the end portion ul of the cut coil piece 30 is connected to the rectifier 12 as a lead wire. Moreover, the end portion u4' of the coil piece 30 is connected to a neutral point in a star three-phase connection among this coil and coils respectively corresponding to other two phases. Thus, a stator 8A is obtained.
Incidentally, although one u2'-u3 connection portion served for crossover connection portion is shown in FIG. 15, the stator has coils respectively corresponding to three phases. Thus, the stator has three crossover connection portions.
In the improved stator coil 16A constructed in this manner, the number of the crossover connection portions is reduced to three.
Thus, the work load of cutting, bending and drawing the coil pieces 30 so as to form the crossover connection portion is alleviated. Consequently, the workability thereof is considerably enhanced.
In this conventional vehicular AC generator, each of constituent phase coils of the stator coils 16 of the stator 8 is constituted by a four-turn coil. The crossover connection portion of each turn is provided at the side opposite to the part connecting the open-end portions 30c. Moreover, the crossover connection portion of each turn protrudes outwardly axially from the coil end portion.
Although the height of the coil end portion at the side of the connecting portion 30b of each of the coil pieces 30 (namely, the dimension of a part projecting from the end surface of the stator core 15) can be reduced, the crossover connection portion of each turn outwardly axially protrudes from the aligned coil end portions, so that the wind resistance at the discharge side of each of the fans increases. Consequently, the total air quantity of the fans decreases, and the cooling ability of the generator is degraded. Especially, when the axial height of the rear-side coil end portion is large, the ability to cool rear-side internal fittings, such as the rectifier 12 and the regulator 18, is adversely affected.
Furthermore, unaligned large coil end portions are placed at the discharge side of the fans. Thus, the conventional vehicular AC generator has a problem in that higher-order discomfort interference noises are generated between the coil end portion and the fan 5 or the coil end portion and the shoulder of each of the claw-like magnetic pole piece 23 of the pole core 21 and that thus, wind noises are loud.
Moreover, the conventional vehicular AC generator has another problem in that it is necessary for connecting 4-turn coils to cut, bend and draw the coil pieces 30 and that thus, the workability thereof is extremely deteriorated.
Additionally, the conventional vehicular AC generator has another problem in that, owing to vibrations thereof, a break is liable to occur in the crossover connection portions and that thus, the risk of power-generation failure is increased.
On the other hand, in the stator coil 16A of the improved stator 8A, the number of the crossover connection portion between four-turn coil constituting each of constituent phase coils is reduced to one. Thus, the work load of cutting, bending and drawing the coil pieces 30 so as to form the crossover connection portion is alleviated. Consequently, the workability in winding the stator coil is considerably enhanced. However, in the stator coil 16A, apex portions 30d of the connecting portions 30b of the coil pieces 30 are axially stacked as two layers and are circumferentially arranged, so that the height of the coil end portion is large and the wind resistance at the discharge side of each of the fans increases. Consequently, the total air quantity of the fans decreases, and the cooling ability of the generator is degraded.
Furthermore, the apex portions 30d of the connecting portions 30b are axially stacked as two layers, so that inner connecting portions 30b are covered by outer connecting portions 30b. Thus, in the soldering process of the open-end portions of the coil pieces 30, even if the stator core 15 is chucked and a plane jig is held to the apex portions 30d of the connecting portions 30b, the open-end portions 30c thereof are of unequal height. In this case, even if the length of the leg portions of each coil piece 30 is preliminary adjusted so as to be able to make the open-end portions 30c of uniform height by holding the plane jig to the apex portions 30d of the connecting portions 30b, the open-end portions 30c thereof are of unequal height as the plane jig is not in contact with the apex portions 30d of the inner connecting portions 30b. Consequently, as the inner coil pieces 30 are soldered in such an unstable condition, the workability in soldering between the open-end portions 30c, that is, the workability in winding the stator coil is extremely deteriorated.